Two restrictions in the theories that include G(t) and c(t) varying with time

Much work has been done taking into account the possibility that the gravitational {\it constant} $G$ may vary with cosmological time $t$ (or with the cosmological scale factor $a(t)$). In many of these works the speed of light $c$ is not addressed or is taken as constant (see for example the Dirac large number hypothesis, \cite{Dirac}). The same can be said of many works that assume the speed of light $c$ to vary with cosmological time $t$ or $a(t)$ (see for example \cite{ MaMo}). Again in many of these works the gravitational constant $G$ is not addressed or is taken as constant. We have two important remarks on these assumptions.Fullana Alfonso, MJ.; Alfonso-Faus, A. (2014). Two restrictions in the theories that include G(t) and c(t) varying with time. Astrophysics and Space Science. 350(2):781-783. doi:10.1007/s10509-014-1803-47817833502Belinchón, J.A., Alfonso-Faus, A.: A theory of time-varying constants. Int. J. Mod. Phys. D 10, 299 (2001). Preprint: arXiv:gr-qc/0404044Dirac, P.A.M.: The cosmological constants. Nature 139, 323 (1937)Magueijo, J., Moffat, J.W.: Comments on “Note on varying speed of light theories”. Gen. Relativ. Gravit. 40, 1797 (2008). Preprint: arXiv:0705.450